We used the upland field rotated from matured rice paddy field, which have been used as a rice paddy field long time, for three years from 2015 to 2017. Therefore, this study was conducted for three main purposes. The first was to investigate yearly changes of growth and yield for waxy maize in the organic farming waxy maize at rice paddy-upland rotation system, the second was to investigate yearly changes of soil physical and chemical characteristics of rice paddy field soil in organic farming waxy maize at rice paddy-upland rotation system and the third was to select the suitable varieties for organic farming waxy maize at rice paddy-upland rotation. The test varieties were that 8 varieties of waxy maize of Mibaek 2, Ilmichal, Daehakchal, Chalok 4, Miheukchal, Eolrukchal 1, Heukjinjuchal, Heugjeom 2. For yearly yield, the highest yield was obtained in the first year of 949.6 kg, the second highest was in the third year of 680.6 kg 10a-1, while the second year was the lowest yield (675.4 kg 10a-1). Both varieties of Chalok 4 and Ilmichal showed the highest yield with about 900 kg 10a-1 in the threeyear average of 8 varieties. Solid phase of deep soil was 10% higher than that of top soil. Porosity rate of the top soil (54.7%) was higher than that of deep soil (49.4%), and the porosity in the third year was 2.7% higher than that of the first year. Soil organic matter content was significant different between soil depths and between three years. Soil solid and liquid phase decreased by 1.6% and 4.3%, respectively, compared to the first year, and the gas phase increased by 4.3%. The porosity of the third year was 2.7% higher than that of the first year. The soil organic matter content was 9.5 g kg-1 in the third year compared with 12 g kg-1 in the first year. It has also trend to decrease as the number of years rotated from rice paddy field increased. In the three-year average yields of Ilmichal and Chalok 4 were 898.1 kg 10a-1 and 891.6 kg 10a-1 respectively and the yield of Chalok 4 was greater than the other 7 varieties. We compared and selected the two best waxy maize varieties of Chalok 4 and Ilmichal for rice paddy-upland rotation. When we look at the yearly variation for waxy maize, Waxy maize yield was the highest in the first year and decreased year by year. Therefore, it would be better to restore upland field to rice paddy fields after the first year.

Paddy-upland rotation system is one of the important cropping system for improving soil quality and crop productivity. we conducted to investigate the effect of paddy-upland rotation system on soil properties and crop productivity in reclaimed tidal land. The paddy-upland rotation could be effective to conserve soil water contents and prevent from salt damage when cultivating upland crops. The first two years of maize cultivation after rice cultivation could be effective to secure stable production. However, in case of soybean crop, the rotation effect might be lower than that of maize. In the first year, the yield of soybean was 214 kg/10a. In the second and third year, the yields of soybean decreased consecutively to 152, 123 kg/10a respectively. In this paper, it would be suggested that maize be cultivated for up to two years and soybean be cultivated for one year after rice crop grown in reclaimed tidal land. This study could be provide basic data of the physico-chemical properties applicable to paddy-upland rotation system at reclaimed tidal lands.

In order to develop optimum paddy-upland rotation system, we evaluated the 1st and the 2nd upland growth and yield characteristics of foxtail millet, proso millet, sorghum rotated from paddy field and rice rotated from upland in paddy-upland rotation. Average number of ears per hill was 3.3 in the 2nd upland cultivation. The value was greater by 1 ear as compared to 1st upland cultivation (2.2 ears per hill). In average yield per 10a, the 2nd upland cultivation showed 220.3 kg, 23% increased yield compared to the 1st upland cultivation (179 kg per 10a). In average number of ears per hill, the 2nd upland cultivation showed 8.3 ears, increased 4 ears compared to the 1st upland cultivation (4.2 ears per hill). In average yield per 10a, the 2nd upland cultivation showed 152.8 kg, 16.8% increased yield compared to the 1st upland cultivation (130.8 kg per 10a). In average days from seeding to heading of 5 sorghum varieties, there were no significant difference between the 1st (68.6 days) and the 2nd (67.4 days) upland cultivation rotated from paddy field. In the average number of grains per ears, the 2nd upland cultivation showed 2,931.6 grains per ear, 12% increased compared to the 1st upland cultivation (2,619.6 grains per ears). Average yield per 10a of sorghum in the 2nd upland cultivation showed 242.3 kg, 4.6% increased compared to the 1st upland cultivation (231.7 kg per 10a). In growth and yield characteristics of rice in paddy-upland rotation, culm length in paddy-upland-paddy plot showed 82.9 cm, 7.3 cm longer compared to the continuous rice paddy field (75.6 cm). Ear length was also 1 cm longer than that of the continuous rice paddy field. In average number of ears per hill, paddyupland- paddy plot showed 25.0 ears, 4.3 ears more than that of the continuous rice paddy field (20.7 ears per hill). In average yield of rice per 10a, the paddy-upland-paddy rotation plot showed 526.8 kg, 9.8% higher yield compared to the continuous rice paddy field (479.9 kg per 10a).